KR20160048995A - Method for forming three-dimensional anchoring structures on a surface by propagating energy through a multi-core fiber - Google Patents

Abstract

A method is provided for forming three dimensional anchoring structures on a surface. This method can result in a thermal barrier coating system exhibiting improved adhesion to its constituent coatings. The method includes the steps of passing a first laser beam (20) through a first portion (7) of a multi-core fiber (4) to a solid material (14) to form a liquefying bed (16) Core fiber 4 to cause a disturbance such as a lump 28 of liquefying material outside the liquefying bed 16, followed by applying to the surface 12 of the multi- Applying a pulse of laser energy (24) to a portion of the liquefying bed (16) through a second portion (6) of the liquefying bed (16). Thereby, a three-dimensional anchoring structure 30 can be formed on the surface 12 upon solidification of the liquefied material's bump shape 28.

Description

METHOD FOR FORMING THREE-DIMENSIONAL ANCHORING STRUCTURES ON A SURFACE BY PROPAGATING ENERGY THROUGH A MULTI-CORE FIBER BACKGROUND OF THE INVENTION 1. Field of the Invention [0001]

Aspects of the present invention relate to thermal barrier coating systems for components that are exposed to high temperatures, such as components facing the environment of a combustion turbine engine. More particularly, aspects of the present invention relate to a laser beam that propagates through a multi-core fiber that forms three-dimensional anchoring structures on a surface. ≪ RTI ID = 0.0 > laser irradiation < / RTI > These anchoring structures provide improved adhesion to the thermal barrier coating system applied across the surface.

It is known that the efficiency of a combustion turbine engine is improved as the combustion gas ignition temperature is increased. However, as the ignition temperature increases, the high temperature durability of the turbine components must correspondingly increase. Nickel and cobalt based superalloy materials are used for components of the hot gas flow path, such as combustor transition pieces and turbine rotating blades and fixed vanes , But these superalloy materials also can not withstand long-term operation at temperatures sometimes exceeding 1,400 ° C.

In many applications, a bond coating (e.g., of a component) on a metal substrate or a metal substrate is used to reduce the operating temperature of the metal substrate and the temperature at which the metal is exposed, Coated with a ceramic insulating material such as a thermal barrier coating (TBC).

TBCs have played a significant role in reducing the operating temperature of turbine components and realizing improvements in turbine efficiency. Obviously, the thermal barrier coating protects the substrate only while the coating remains substantially intact on the substrate surface.

During operation, the TBCs and any underlying bond coatings undergo spallation and degradation. The causes of these distresses are: foreign objects, differential thermal expansion (i.e., between the underlying superalloy substrate and the overlying bond coat or between the bond coat and the TBCs), material defects And high physical stresses caused by high velocity ballistic impacts due to material property changes due to the operating environment. Either of these situations can lead to bond coating and / or damage and even complete removal of the TBC from the substrate surface. Conventional repair processes include peeling off the damaged layer (s) and recoating the substrate, which is a time-consuming and costly operation.

It is known to control the roughness parameter of the surface (e.g. the substrate surface) to improve the adhesion of the overlying bonding layer or thermal barrier coating. U.S. Patent No. 5,419,971 discloses a laser ablation process in which the removal of material by direct evaporation (e.g., without melting the material) is used as is known to form three-dimensional features on the surface to be irradiated ) (See row 6, line 3). These features are limited to the patterns formed in the surface being irradiated. These laser ablation processes do not form structures that extend beyond the surface. Thus, there is a need for processes that can provide improved structural configurations that help improve adhesion.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is illustrated in the following description with reference to the drawings, which show:
1 is a cross-sectional view of a solid material that is irradiated by laser irradiation in accordance with aspects of the present invention.
Figure 2 is an isometric view of an exemplary bounce shape of a liquefying material that forms three dimensional anchoring structures on the surface of a solid material upon solidification of a material splash, in accordance with aspects of the present invention.
Figure 3 is a partial cross-sectional view of a non-limiting example of anchoring structures such as undulations, waves, fingers, or hooks formed on the surface of a solid material.
4 is a partial cross-sectional view of an exemplary gas turbine component including a thermal barrier coating system that can benefit from a method of implementing aspects of the present invention.
5 is a partial cross-sectional view of a thermal barrier coating system in which the bond coat surface can undergo laser irradiation in accordance with further aspects of the present invention.

According to one or more embodiments of the present invention, three-dimensional anchoring structures (usually referred to as mechanical hook shapes, finger shapes, or wave shapes) are formed on surfaces exposed to laser irradiation from multi- Structural arrangements and / or techniques that aid in forming the shape and / or dimensions of the device are described herein. In one application, the mechanical hook shapes can improve the adherence of the bond coats and TBCs on the gas turbine blades and vanes, and can also extend the duration of the effective TBC. The techniques of the present invention can be used during the manufacture of blades and vanes and also during maintenance. In either case, the operating life of the blades and vanes is prolonged.

The inventors of the present invention propose a breakthrough application of laser irradiation from multi-core laser fibers to form three-dimensional anchoring structures on the surface of a substrate or bond coat. The multi-core coaxial fibers 4 as comprising the inner core 6 and the outer annulus 7 are illustrated in the axial section of Fig. According to one embodiment, a relatively higher power laser is propagated in the inner core 6, and a laser of lower power is propagated in the outer annulus 7. When exiting the fibers 4, both laser beams strike the surface 12 of the solid material or substrate 14.

In one embodiment, the outer laser beam 20 (pulsed or persistent) propagating through the outer annulus 7 is melted (as shown in FIG. 1) 16 (a liquefied bed ), ≪ / RTI > of relatively high power density, which produces a relatively large diameter beam. As the optical components and the substrate 14 are moved relative to each other, a plurality or series of such fusions 16 are formed on the surface 12, as indicated by the arrowhead shape 18.

The inner pulsed laser beam 24 carried by the inner core 6 exhibits a relatively higher power density and a narrower beam diameter than the outer laser beam 20. [ The inner laser beam 24 is focused at least on the area of the melt 16 to create a disturbance in the melt 16. For example, illuminating the melt 16 with the inner laser beam 24 before the melt 16 is solidified creates a bouncing shape of the liquefied molten material. This bump shape can be formed on the outside of the melt 16 and / or on the melt 16. When the bump shape is solidified, anchoring surface features or structures 30 (e.g., hook-shaped, anchor-like or finger-like structures) are formed. These structures serve as anchors to mechanically improve the adhesion of the TBC or bond coat layer, which is later applied on the surface 12 of the substrate 14. [

Generally, the melt may be about 1 to 4 mm in diameter or width, and the splash-like or anchoring structures extend up or out of the melt by about 10 to 30 percent of the melt diameter.

These multi-core coaxial laser fibers 4 and associated core switching devices for use in accordance with the present invention may be used in a variety of laser manufacturers, such as those manufactured by Trump Corp. < RTI ID = 0.0 >Lt; / RTI > (Trumpf, Inc.). These multi-core laser fibers are produced by cutting the material with a laser propagated through a 100 micron diameter core and then welding the material with a laser propagating through a circular body of 400 or 600 microns in diameter , But have been used for alternate processes rather than concurrent processes.

FIG. 2 illustrates a solidified bump shape 28 including three-dimensional hooked anchoring structures 30 outwardly of the liquefying bed 16.

FIG. 3 illustrates a solidified bump shape 34 having features different from the solidified bump shape 28 of FIG. In particular, the bouncing feature 34 includes a wave-like anchoring structure 36 in addition to the finger-like anchoring structure 30.

Generally, hook and finger anchoring structures have similar structural features. The wavy anchoring structures tend to show smoother surface features that do not necessarily provide the same mechanical advantages as those provided by hook shapes / finger shapes. Still, the wave shapes increase the attachment surface area and thus withstand any lateral shear forces applied on the TBC or bond coat. Due to better adhesive properties, claw shapes / finger shapes are typically preferred over wavy shapes.

The configuration of wavy shapes or hooked / finger shaped anchoring structures is generally a function of the amount and timing of laser energy applied to the melt. Formation of claw shapes / finger shapes generally requires more energy than forming wavy shapes.

According to one embodiment, the outer laser beam 20 is controllably defocused to a desired depth into the substrate or bond coat layer to cause the melt 16 to expand only to an exemplary depth of, for example, about 0.3 mm can be defocused or power-controlled.

The inner laser beam 24 has a sufficiently high power density to form a disruption in the melt 16, such as the anchoring structures 30 of Figure 2 or the wave shape 36 of Figure 3, (Pulse). The configuration of the disruption may be due to localized instantaneous evaporation of the metal material.

In one non-limiting embodiment, the typical energy density for a typical large area of melting (i.e., to form melt 16 by outer laser beam 20) is from about 3 kJ / cm ² to about 10 kJ / cm < ² >.

In the case of disruption of the melt 16 to create the hooked anchoring structures 30, pulses of focused energy may be used. In one non-limiting embodiment, such pulses may include parameters with respective ranges of typical of laser ablation processing. Karl-Heinz Leitz et al., Physics Procedia, Vol. In a paper entitled " Metal Ablation with Short and Ultrashort Laser Pulses ", published in 12, 2011, pages 230-238, these ranges in parameters are summarized as follows:

The disruption (e.g., bouncing shape) of the liquefied material formed in the liquefying bed 16 can also be a function of the liquefied bed 16, such as sonic energy, ultrasonic energy, mechanical energy (e.g., air puff of air, Can be generated by energy pulses other than laser energy.

According to another embodiment, the laser and sonic, ultrasonic, or mechanical energy propagating through the annular region of the fiber is carried through the hollow core. In one embodiment, the outer diameter of the fibers is, for example, about 600 microns, and the hollow core has a diameter of, for example, about 200 microns.

The laser energy produces a melt 16. In one embodiment, a wire of high melting point material (e.g., carbon), e.g., a wire of diameter 190 microns, is passed through the core and / Is gradually inserted into the melt (16).

Alternatively, other forms of mechanical energy such as bursts of air, sonic energy, or ultrasonic energy may be carried through the hollow core.

The above-described processes, which are variously described, can be repeatedly performed throughout the surface 12 to form a large number of three-dimensional anchoring structures 30 on the surface 12. [ Moreover, the three-dimensional anchoring structures 30 may be selectively distributed throughout the surface 12. For example, surface areas that are expected to face relatively large levels of stress may have a greater number of three-dimensional (3D) dimensions per unit area, as compared to surface areas that are expected to experience relatively lower levels of stress May be manipulated to include anchoring structures (30).

In addition, a pulse of laser energy 24 is focused onto such selected area (s) to form anchoring structures 30 in selected areas (s) of melt 16.

In one non-limiting embodiment, the laser beams 20 and 24 may be used to scan a substrate 14 (e.g., a laser beam) in accordance with the use of a beam-scanning technique (e.g., two-dimensional scanning) (Not shown). Such beam scanning may proceed not only in the direction designated by arrowhead shape 18 in FIG. 1, but also in a direction perpendicular to arrowhead shape 18 along surface 12.

In addition to the movement of the multi-core coaxial fibers 4 (and thus of the laser beams 20 and 24) across the fixed substrate, the fixed fibers and the laser beams propagated through the fibers Can be moved. Thus, during the scanning process, the fibers 4 are moved relative to the substrate 12, or the substrate 12 is moved relative to the fibers 4.

In an alternative embodiment, the pulse of the laser energy 24 (i.e., the inner laser beam) that causes the bump shape is applied during application (i.e., forming a melt) of the outer laser beam 20 to the surface 12 It can be authorized interspersedly. For example, at a specific time during the application of the inner laser beam 20, the pulse of the laser energy 24 is applied to a given spot in order to cause a jumping profile, May be focused onto a given spot of the liquefying bed 16 to form an anchoring structure 30.

Alternatively, the inner laser beam 24 may be energized immediately before or after the deactivation of the outer laser beam 20. [ For example, in one embodiment, the time interval between deactivation of the outer laser beam 20 (which forms a melt) and energizing of the inner laser beam 24 (which forms the protrusion shape) is less than 1 second a fraction of a second, such as 0.5 seconds.

The processes described herein may be performed by passing the laser beam 20 across the surface 12 (or by relative movement therebetween) to form a melt pool 16 that continues to travel, And the pulsed energy 24 is applied repeatedly near the moving trailing edge of the molten pool 16 just before the material is re-solidified. This process is effective in creating a plurality of anchoring structures across the surface as the surface is re-solidified.

Those skilled in the art will recognize that the laser beams 20 and 24 (e.g., power and focus) can be controlled to achieve anchoring structures 30 of desired full depth and desired dimensions.

It is contemplated that an appropriate enclosure may be used to control the environmental conditions of the method while performing the above-described laser irradiation processes. For example, depending on the requirements of a given application, one may choose to perform the laser irradiation process under vacuum conditions instead of air pressure, or may choose to inject an inert or reactive gas into the environment instead of air.

Fluxes represent another alternative to the use of inert shielding gases. The flux can be applied to the surface 12 before activation of the laser beams 20 and 24. The molten flux is attached to the protruding shaped material to protect the anchoring structures 30 from environmental contaminants as the anchoring structures 30 are cooled and solidified. The flux is then removed by any of well-known techniques such as mechanical brushing processes, grit blasting, and the like.

In one non-limiting application, a method of implementing aspects of the present invention includes the steps of providing thermal protection of a component 42 (FIG. 4) (e.g., blade, vane, etc.) operating in a high temperature environment of a gas turbine engine (Or repair) a barrier coating system. The component 42 may be a metal substrate 44 covered by a barrier coating, such as a layer of a ceramic thermal barrier coating (TBC) 46, for use in a high temperature environment of a turbine engine ).

Prior to application of the TBC 46 to improve the adhesion of the TBC 46 to the substrate 44, a bond coat 48 (e. G., ≪ RTI ID = , MCrAlY material) may be deposited on the substrate 44.

It will be appreciated that aspects of the present invention are not limited to the exemplary coating arrangement shown in Figure 4, nor are these aspects limited to components having a TBC coating or bond coating.

In one non-limiting application, the surface of the solid material subjected to laser irradiation to form the three-dimensional anchoring structures on its surface may be the metal substrate 44. Next, in constructing these three-dimensional anchoring structures, the bond coat layer 48 may be deposited on the surface of the metal substrate 44 including the three-dimensional anchoring structures. Thus, in such applications, the bond coating may be anchored by three dimensional anchoring structures (e.g., superalloy anchors), and the bond coating may be metallurgically integrated with the substrate 44.

In other non-limiting applications, referring to FIG. 1, the surface 12 of the substrate 14 may comprise a bond coat. Next, in constructing the three dimensional anchoring structures, a layer of TBC 46 (see FIG. 4) may be deposited on the surface of the bond coat comprising three dimensional anchoring structures. Thus, in such applications, the TBC 46 may be anchored by three dimensional anchoring structures (e.g., bond coating anchors) and the TBC 46 may be metallurgically integrated with the bond coating 48.

In yet another non-limiting application, the metal substrate and then the respective surfaces of the bond coat may be subjected to respective laser irradiation to form three-dimensional anchoring structures on both of these surfaces. For example, the surface of the metal substrate 44 may first be subjected to laser irradiation to form three-dimensional anchoring structures on its surface. A bond coat layer 48 is then deposited on the surface of the metal substrate 44 including the three dimensional anchoring structures. The top of the anchoring structures formed on the metal substrate 44 are then typically subjected to laser irradiation without direct laser exposure to form three dimensional anchoring structures on the surface of the bond coat 48, The surface can be subjected to laser irradiation. Next, finally, a layer of TBC 46 may be deposited on the surface of the bond coat including the three dimensional anchoring structures. Thus, in such applications, the bond coating may be anchored by three-dimensional anchoring structures (e.g., superalloy anchors), and the bond coating may be metallurgically integrated with the substrate 44. In addition, the TBC 46 will be anchored by three dimensional anchoring structures (e.g., bond coating anchors) and the TBC 46 will be metallurgically integrated with the bond coat 48.

In one non-limiting embodiment, assuming that the surface of the solid material subjected to laser irradiation to form the three-dimensional anchoring structures on its surface is the bond coat 48, as illustrated in Figure 5, It may be desirable to control the depth D of the liquefying bed 16 so that the bed 16 does not extend into the substrate 44. [ For example, the area T1 of the solid bond coat 48 (e.g., the unmelted layer of the bond coat 48) is held between the boundary with the substrate 44 and the bottom surface of the liquefying bed 16. In one non-limiting embodiment, the thickness T2 of the bond coat 48 may range from about 150 micrometers to about 300 micrometers and the unfused region T1 may have a thickness T2, About 10% to about 50% of the total weight of the composition.

In different applications, the melt size may be increased or decreased as required depending on the use of corresponding larger or smaller size fibers and / or higher or lower power lasers. Larger or smaller anchor features with selective spacing of finger shapes or hook shapes may be formed in accordance with the use of higher or lower power densities of lasers and / or larger or smaller diameter fibers.

Although described in the context of dual fibers, according to another embodiment, more than two propagation media may be used, such as triple core fibers. These separate beams can also be used to create segmented mirrors to produce different beams for individual functions including, for example, less intense heating for deep melting and stronger heating for surface dislocations. Lt; RTI ID = 0.0 > fibers. ≪ / RTI >

Conventional superalloys for use in the preferred embodiment of surface modification are CM 247, Rene 80, Rene 142, Rene N5, Inconel-718, X750, 738, 792 and 939, PWA 1483 and 1484, C263, ECY 768, CMSX- 4 and X45 (but are not limited to).

Various laser types for use in accordance with the present invention include, but are not limited to, NdYAG, ytterbium fiber, and laser diodes.

According to one embodiment, the laser beam 20 (see FIG. 1) for producing the molten pool 16 may have a different frequency than the laser beam 24 for generating the splash feature 28. These individual frequencies can be selected to provide optimal efficient operation of the laser beams 20 and 24 in their respective feature configurations. For example, the laser beam 20 may have an optimal frequency for coupling with a solid surface, while the laser beam 24 may be used for coupling with a molten surface to cause a protruding shape It can have an optimum frequency. In addition, the laser beams 20 and 24 may have different "on" durations (i.e., lasing durations) to form their respective features.

In the foregoing detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention and various embodiments of the invention. However, those skilled in the art will appreciate that embodiments of the invention may be practiced without these specific details, and that the invention is not limited to the embodiments shown, and that the invention may be practiced in various alternative embodiments . In other instances, methods, procedures, and components that will be well understood by those skilled in the art are not described in detail in order to avoid unnecessary and cumbersome explanations.

In addition, the various operations are described as a number of separate steps performed in a manner that aids in understanding embodiments of the present invention. However, the order of description should not be construed as to imply that such operations should be performed in the order in which they are presented, nor should they be interpreted to mean that the operations are order dependent unless otherwise stated. Moreover, the repeated use of the phrase "in one embodiment " may refer to the same embodiment, but is not necessarily referring to the same embodiment. Finally, terms such as " comprising ", " comprising ", "having ", and the like, as used herein, are intended to be equivalent unless the context clearly dictates otherwise. Accordingly, the invention is intended to be limited only by the spirit and scope of the appended claims.

Claims (20)

As a method,
Propagating a first laser beam through a first fiber of a multi-core fiber and a second laser beam through a second fiber of the multi-core fiber;
Applying the first laser beam onto the surface to form a liquefied bed on a surface of the substrate;
Applying the second laser beam to at least a portion of the liquefying bed to cause a splash of liquefying material outside the liquefying bed; And
Forming a three-dimensional anchoring structure on or in the surface of the substrate upon solidification of the bouncing shape of the liquefying material,
/ RTI >
Way. The method according to claim 1,
Wherein the three-dimensional anchoring structure comprises at least one of a hook, a finger, and a wave,
Way. The method according to claim 1,
Wherein applying the first laser beam and the second laser beam comprises scanning the first laser beam and the second laser beam against a surface of the substrate,
Way. The method according to claim 1,
Wherein the step of applying the second laser beam is performed during the step of applying the first laser beam.
Way. The method according to claim 1,
Wherein the first laser beam comprises a continuous laser beam or a pulsed laser beam, and
Wherein the second laser beam comprises a pulsed laser beam,
Way. The method according to claim 1,
Providing one of an inert gas, a reactive gas, or vacuum conditions around the surface during the applying steps
≪ / RTI >
Way. The method according to claim 1,
Applying a flux to the surface before applying the first laser beam to the surface
≪ / RTI >
Way. The method according to claim 1,
The parameters of the first and second laser beams include a lasing duration, a power density, and power,
Wherein at least one of the parameters is different between the first laser beam and the second laser beam,
Way. The method according to claim 1,
The first laser beam propagates through the annular region of the multi-core fiber to exhibit a relatively lower power density and a relatively larger diameter beam, and
Wherein the second laser beam is propagated through an inner region of the multi-core fiber to exhibit a relatively higher power density and a relatively smaller diameter beam,
Way. The method according to claim 1,
Wherein the first laser beam is controlled to cause melting to a selected depth of the surface,
Way. The method according to claim 1,
Wherein the substrate comprises a gas turbine vane or a blade,
The method comprises:
Forming an anchoring structure on a bond coating layer or a ceramic thermal barrier coating layer of the substrate;
≪ / RTI >
Way. As a method,
Applying energy having a first power density to the surface of the solid material through an annular region of the multi-core fiber to form a liquefied bed on the surface of the solid material;
Applying a pulse of energy having a second power density greater than the first power density through an inner core region of the multi-core fiber to cause disruption of at least a portion of the liquefying bed ; And
Allowing the disruption to solidify on the surface of the solid material to form an anchoring structure
/ RTI >
Way. 13. The method of claim 12,
Wherein the anchoring structure comprises at least one of a hook shape, a finger shape, and a wavy shape,
Way. 13. The method of claim 12,
The pulse of energy comprises a pulse of laser energy, and
Wherein the disruption comprises a protruding shape of the liquefying material on the outside of the liquefying bed,
Way. 13. The method of claim 12,
Wherein the pulse of energy comprises a pulse of ultrasound energy or a pulse of sonic energy,
Way. 13. The method of claim 12,
Applying a flux to the surface before applying energy having the first power density
≪ / RTI >
Way. As a method,
Providing first and second energy sources;
Transferring a pattern of energy from the first source by scanning a surface of the solid material to create a moving pool of re-solidifying liquefied material along a trailing edge, Energy from the first source is transmitted through the annular region of the multi-core fibers; And
The pulses of energy from the second energy source are repeatedly applied to the pool of liquefying material with pulses of energy from the second energy source to create a respective plurality of anchoring structures across the surface as the pool of liquefied material moves and the surface is re- Stimulating Step
Lt; / RTI >
Wherein the energy from the second source is transmitted through the inner region of the multi-
Way. 18. The method of claim 17,
The solid material is a bond coat of a thermal barrier coating system,
The method comprises:
Controlling a pattern of energy from the first energy source such that the depth of the moving pool is less than the thickness of the bond coat
≪ / RTI >
Way. 18. The method of claim 17,
Wherein the first and second energy sources comprise first and second laser energy sources,
Way. 18. The method of claim 17,
Wherein the inner region of the multi-core fibers comprises a hollow inner region, and
The pulses of energy include pulses of ultrasonic energy, pulses of sonic energy, or pulses of mechanical energy.
Way.

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